Many transmission systems such as continuously variable transmissions (CVTs) employ a torque controlling element to provide a continuously variable torque or speed transmission capability. An example of such a transmission is a split torque transmission, wherein a drive train is powered by dual inputs, one of which may be a torque-controlled input, such as from a hydraulic variator. In such systems, it is desirable to accurately control the variator such that the resultant actual operation of the system based on control signals corresponds to the expected operation of the system. For example, a discrepancy between the expected and actual operation of the system may result in deteriorated shifting performance resulting in operator discomfort, system inefficiency, and/or increased drive train wear.
In attempting to reduce this problem, a number of systems utilize a calibration or torque control map that links an input pressure or pressure differential to an output torque of the variator. Nonetheless, under actual operating conditions, some entries in the torque control map may be erroneous or may become erroneous due to the gradual wear of components, play or slop in the control system, and so on, thus still leaving an often significant discrepancy between the expected and actual operation of the system.
The foregoing background discussion is intended solely to aid the reader. It is not intended to limit the innovation, and thus should not be taken to indicate that any particular element of a prior system is unsuitable for use within the described and/or claimed system, nor is it intended to indicate any element, including solving the motivating problem, to be essential in implementing the innovations described herein. The implementations and application of the innovations described herein are defined by the appended claims.